Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 4:17 PM GMT on August 15, 2009

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Tropical Storm Ana was born this morning, when the remnants of Tropical Depression Two made a comeback and organized into the first tropical storm of the 2009 Atlantic hurricane season. Ana is the latest first named storm of the season since Hurricane Andrew got its name on August 17, 1992. The two storms have some similarities, as Andrew formed in the same part of the ocean, and also struggled in its early days with high wind shear and dry air. Let's hope the similarities end there.

Ana is struggling this afternoon. After an modest burst of heavy thunderstorm activity prompted NHC to upgrade Ana to a tropical storm early this morning, Ana has run into strong upper-level winds from the west that are creating high wind shear. This shear was not forecast, and it is not clear how long it will last. The shear has acted to drive dry air into the core of Ana, destroying almost all of Ana's heavy thunderstorms. The low-level center of the storm is now exposed to view, something that often foreshadows the death of a storm. It is possible the shear will destroy Ana, and several models (the GFS and ECMWF) forecast this may be the case. However, the shear forecast calls for shear to drop into the low range, 5 - 10 knots, tonight through Tuesday. If the shear does drop as forecast, Ana should be able to moisten the atmosphere around it sufficiently to protest itself from the dry Saharan air that surrounds it (Figure 1). SSTs are 27°C today, and will increase to 28°C by Sunday. By the time Ana moves into the Bahamas, total ocean heat content rises steeply (Figure 2), and rapid intensification of Ana is possible, if the shear and dry air haven't disrupted the storm. The intensity forecast models, for the most part, predict a steady intensification of Ana to the threshold of hurricane strength five days from now. The HWRF model is on the strong side, predicting a Category 2 hurricane. The GFDL predicts a weak tropical storm five days from now, but that is because the model has Ana passing over the rugged terrain of Hispaniola, something the other models do not predict. In summary, the intensity forecast for Ana has higher than usual uncertainty, and I give equal chances that the storm will be a hurricane--or non-existent--four days from now.


Figure 1. Water vapor image from this morning showing the large area of dry, Saharan air surrounding Ana, and lying to the north of Tropical Depression Three. Image credit: NOAA/SSD

Tropical Depression Three forms, could be Bill later today
QuikSCAT data from this morning and satellite loops revealed that the tropical wave (90L) in the middle Atlantic has finally developed a well developed surface circulation and can be classified as Tropical Depression Three. Recent satellite imagery suggests that TD 3 may already be Tropical Storm Bill. Water vapor imagery (Figure 1) shows that TD 3's center consolidated a few hundred miles south of the dry air of the Saharan Air Layer (SAL). Thus, the storm should not be affected by dry air and dust as much as Ana has been. Ana may also act to moisten the atmosphere in front of TD 3, helping protect the storm from the SAL as it edges farther north over the the three days.



Figure 2. Heat content of the ocean, in kJ per square cm. Oceanic heat content steadily increases for Ana and TD 3 as they approach the Lesser Antilles Islands. Oceanic heat content levels of 90 kJ per square cm are frequently associated with rapid intensification of hurricanes. Image credit: University of Miami.

Wind shear is moderate, 15 knots, but is forecast to fall to 10 - 15 knots on days 2 - 5. Sea Surface Temperatures are about 27.5°C, and will remain in the 27.5 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow TD 3 to intensify steadily, and I expect the storm will be at hurricane strength by Wednesday, when it will be near the northern Lesser Antilles Islands. Most of our reliable intensity models strengthen TD 3 into a hurricane by Wednesday. Oceanic heat content (Figure 2) increases sharply just before the islands, so TD 3 could be intensifying rapidly as it moves through or just north of the Lesser Antilles on Thursday. TD 3 consolidated farther south than expected, so the track models calling for a more northerly path were probably incorrect. In particular, the ECMWF model, which had TD 3 turning sharply northwestward and missing the Lesser Antilles Islands, was probably much too far to the north in this morning's 00Z run. TD 3 will probably pass very close to the northern Lesser Antilles islands on Wednesday and Thursday.

I'll have an update Sunday.

Jeff Masters

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Wow i see we have 91L in the GOM now.
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3012. jipmg
Quoting Grothar:
Link

If Bill is supposed to make a turn. Can anyone explain this from th NHC. The cone is the 11:00 PM advisory. Any please care to comment


models are saying bill is/should be moving NW or WNW right now, instead its moving due west or just south of due west, so the NHC doesnt seem to be trusting the models completely right now
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Quoting PcolaDan:

Aren't you getting a headache though from all the head banging though? Have on on me.


I like that one..and I will thank you.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
3010. jpsb
Quoting CatastrophicDL:

Upper right hand of the comments section - adjust your filter.
Thank You!
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3007. Grothar
Link

If Bill is supposed to make a turn. Can anyone explain this from th NHC. The cone is the 11:00 PM advisory. Any please care to comment
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Quoting superweatherman:
let play the game.... what will be the change of 91L of becoming a TD by tomorrow at 8Pm. I say 70%

50%
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Its such an odd feeling when you look at the radar and see 91L just off the coast, yet see/feel no effects at all in cape coral,fl. calm as can be here... no rain.. no wind.. nothing. Mother Nature is so mysterious.
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3004. flsky
Quoting KEHCharleston:
Bermuda is a pretty small target : )


Insensitive. Bermuda is a target every hurricane season.
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Quoting Orcasystems:


I am a changed person.. nothing but S&I now :)

Aren't you getting a headache though from all the head banging though? Have on on me.
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Quoting nola70119:
I see we have a new invest 91L.
Hey guys how many floaters do we have?
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Quoting superweatherman:
let play the game.... what will be the change of 91L of becoming a TD by tomorrow at 8Pm. I say 70%
I agree with that but not past ts .
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2999. nash28
What's up Adrian and Pat?
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You can also go to the top right hand side of the blog and select to see all. Selecting good, bad etc will filter others comments by others opinions.
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2997. Patrap




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Quoting Patrap:
91L Short Wave IR Image


Have a look at this loop. Look what goes up the west coast of Florida, then watch the train continuing to roll off Africa.
Link
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Do not be startled if we wake up to a surprise in the gulf.
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Quoting presslord:
the 'fishcasters' are as bad as the wishcasters...



Hahaha, Press!!
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Quoting Chicklit:

Great minds think alike.
That was just my exact thought.


Nice !!

Ana continues to hang on. I have never thought that it would amount to much with all the dry air and shear.
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ana will fool all of you who keeps saying she wont be nothing keep thinking that its not always the leaning tree that falls first

just food for thought
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We've all got opinions, as do the models (which imho have not been very consistent whatsoever with Ana and Bill and have shifted greatly, even if they are in an agreement right now, they weren't before and what's to say they will continue to agree).

Past 48 hours, it really is not possible for us to know what's going to happen. All we can do is to watch and see. As for the models again, I will not start to believe them until I see consistency over a few consecutive runs, with the system actually following the track plotted in the model forecast. So with the models currently expecting them to be moving to the WNW and to have them actually going to the W or WSW, doesn't that show you they may not have a great handle on the current situation?

So yes as I said, let's be patient and wait and see. There's no need to panic, and overreact. If you live anywhere from lets say...Hispaniola and the Gulf Coast all the way to the Canadian Maritimes just watch the progress. Because Ana or Bill could easily affect anywhere in between there.


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Good night all. Should see Ana Dead by Morning. Bill Around 60 MPH and TD4 forming around midday
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Bill is hearing the call of the fish.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting jpsb:
Lol, I'll risk it, off topic but why do I have to hit the "show" button to see some posters posts? thanks.


It means a number of people have seen the posts, and clicked on the - sign in the upper right of the comment block
Member Since: October 1, 2007 Posts: 81 Comments: 26511
2985. GatorWX
Shear is also very low in the eastern gulf, something I didn't realize. I thought it was somewhat higher. Only 5-10 kts over 91. HMMMMMMMMMM....
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Quoting jpsb:
Lol, I'll risk it, off topic but why do I have to hit the "show" button to see some posters posts? thanks.

Upper right hand of the comments section - adjust your filter.
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Quoting presslord:


get some help
This time JFV may be right, for real. I not his biggest fan but I have said this for days. I ask this on the Barometer Bob show.
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2982. 19N81W
Hey guys...just wondering what your thoughts are on these two systems in how they will impact on the Cayman Islands and Florida..in particular Tampa. I live in Cayman and going to Tampa on Friday for a weeks vacation! Thanks in advance....
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2981. Patrap
91L Short Wave IR Image

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let play the game.... what will be the change of 91L of becoming a TD by tomorrow at 8Pm. I say 70%
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Quoting KEEPEROFTHEGATE:
i am watchin all night long stormw if i see any sign at all those on here will know



Looking forward to the rain it will bring us here in Florida tomorrow.
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ECM might do it again...We'll see though.Ana might not be an issue as land inter-interaction should keep it in check.
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2975. GBguy88
Where is 91L going in the long term? Northern Gulf Coast here...wouldn't mind a small storm, could use the rain, but not in the mood for a strong one.
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Quoting kmanislander:
Ana continues to underwhelm us. Bill is the one to watch IMO

Great minds think alike.
That was just my exact thought.
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the 'fishcasters' are as bad as the wishcasters...
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NOLA local mets downplayed 91L also.
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nobody knows where these storms are going bill might get into the gulf dont be surprised if things change with the forcast
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Quoting tiggeriffic:
bounced in for just a few...the storms aren't even hurricanes yet and ppl are already at each others throats...let's face the facts...everyone from the islands to the gulf and the entire east coast need to watch these storms...prime example...HUGO! According to the computers Charleston was NOT supposed to get hit...by the time they realized it was headed here...it was pretty much too late to do anything...most were stuck, no supplies, etc...I don't trust the models more than 24-48 hours out...storms jog all the time...besides, they are way too far out to predict anything at this point. (stepping off my soap box now)
I wasn't stuck! I had my hurricane supplies ready in June that year. (And made sure my sisters did too.) Had a succession of wind storm dreams through out the spring of that year. Not psychic, but I do not need to have God hit me on the head too many times before the message comes through.
Seriously, being prepared was a tremendous relief at a very anxiety provoking time.
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Quoting BiloxiGirl:


Hey Fire! Glad to see you. I am looking for the same. That one has my interest right now.


I looked at the loop that winter123 posted. Looks like 91L may be heading WNW for now. My question is probability of development. So far, shear in the GOM is low. 91L does have some circulation to it. SSTs are in the right range for development. Guess we just have to sit and wait. Remember, the big "K" developed in this area. 8-O
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Quoting Nickelback:
Ok for everyone thinking Bill looks Strong (Like Hurricane) is wrong. Yes he's better Organized than Ana but what's really happening is your looking at Bill and you see a "bigger" system compard to Ana. You have to look at more than just its size.

TS Bill

TS Ana

I no which looks better and stronger
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good night everyone. will be interesting in the morning.
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A little info/conversation on 91L:

http://www.canetalk.com/2009/08/1250392862_1250392732.shtml

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Quoting CatastrophicDL:

Yep, you're keeping the halo shiny!


I am a changed person.. nothing but S&I now :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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